1. Field of the Invention
The present invention relates to door locking devices requiring rotation output such as actuators for locking doors of cars or rooms, and especially to a door locking device which is simple in structure, economical, small in noise upon actuating it, and able to provide swing or rotation output fast and smooth.
2. Description of the Related Art
A variety of electric actuators have heretofore been used in door locking devices for cars, rooms and the like. Many of such electric actuators make use of electromagnets. Therefore, they involve a drawback that rasping and loud crashing sound is produced. When used in a door locking mechanism for cars by way of example, such rasping and loud crashing sounds are very uncomfortable. Therefore, in order to reduce the noise of door locking devices, the use of a d.c. motor of a core-equipped structure in a locking device has come to be attempted in recent years.
However, such a door locking device is such that a conventional d.c. motor is simply used as is. A d.c. motor having a structure adapted to the mechanism of the door locking device is not used. Since any d.c. motor with the performance of the device itself, for example, a door locking mechanism for cars or the like, taken into consideration is unknown, the door locking device involves a drawback that it requires a complex structure making use of a multiple gear composed of plural gears and hence becomes large in size and expensive.
In addition, since the structure of such a d.c. motor is poor in efficiency, and is an axial air-gap type core-equipped structure, cogging is produced to a great extent, so that the motor cannot be actuated smoothly and its responsibility is inferior. Moreover, with respect to the door locking device making use of such a d.c. motor, the responsibility is also poor because of the multiple gear used in the motor. Furthermore, it has a drawback that great force is required when the door locking device is operated manually and moreover involves a demerit that it produces a loud noise of release.
Furthermore, since there is a recent tendency for the thickness of car doors to be reduced, so that the space for building in a door locking device is limited, the conventional door locking device making use of the d.c. motor of the core-equipped structure involves a demerit that it is troublesome to successfully dispose it in a door body of a small thickness.